How can I find out what's the bottleneck slowing down a particular process / the entire system?

Given a specific running process, is there a way to find out what hardware element is currently the bottleneck for its operation? In other words, is its current computation CPU-bound, GPU-bound, memory-bound, IO-bound, etc?

Answers that work for Windows XP are preferable, but all answers are welcome.

EDIT: I'm thinking about processes that take the absolutely majority of system resources to themselves; so solutions that can help me find the current battleneck for the entire system (e.g. what element is working hard the most while the others are resting) is fine as well.

EDIT 2: someone has asked me this question and my answer was

Open your task manager and choose to view page faults for the application - a very high count hints that you do not have enough physical memory. Check out the CPU utilization - if it's constantly at 100% it's a sign it may not be fast enough for this real-time application.

That's what I would have done but it feels a bit amateur-ish, so I'm looking for more precise, complete ways to identify the offender.

Oak

Posted 2010-11-10T18:41:08.710

Reputation: 1 255

1Anything less crude than “look at your task manager” is going to be very OS-specific, so I took the liberty of adding an OS tag. – Gilles 'SO- stop being evil' – 2010-11-10T23:07:24.933

@Gilles no problem, I guess it wasn't a good idea to make the question OS-agnostic in the first place. – Oak – 2010-11-11T12:26:50.243

Answers

You can use the Microsoft XPERF tools to walk the stack and find bottle necks. You can only view the results on Vista/7 (or server 2008) but you can run the profile tool on XP. Pigs Can Fly has some really good articles on stackwalking with XPERF.

We used it to find bottlenecks in our boot speed, and finally had proof to show the company to remove some tools that were taking too much Disk IO at boot.

Brian

Posted 2010-11-10T18:41:08.710

Reputation: 2 934

In order to "walk the stack" you're going to need debugging symbols for the application in question. – Billy ONeal – 2010-11-10T18:50:46.683

Yes, but with just the windows debugging tools, you can see what system things it is waiting on, like disk, networking, video drivers, etc, by seeing how much time it spends on those tasks. That can let you know to try a newer driver, or faster disk, etc. – Brian – 2010-11-10T19:02:56.663

You would need to use a profiler. You would probably also need access to the program's source code, or at least to debugging symbols.

Billy ONeal

Posted 2010-11-10T18:41:08.710

Reputation: 7 021

I'm asking about external processes, ones that I have no special access to. Off-the-shelf non-customizable applications. – Oak – 2010-11-10T18:47:26.270

Oak, as far as I know you can't do that. You can measure what's bottlenecking the machine as a whole, but without profiling you're not going to be able to figure out exactly what any particular process is doing (and you need the debugging symbols for that) – Billy ONeal – 2010-11-10T18:50:08.977

@Billy Thanks for explaining. Measuring the bottleneck on the entire system is actually fine for me; I've edited my question accordingly. – Oak – 2010-11-10T18:53:58.120

@Oak: Ok, if the bottleneck is disk related, then look at the HDD activity light on your machine. If it's constantly lit, it's disk bottlenecked. Look at task manager - if CPU is maxed out, then it's CPU limited. If physical memory is full, that is also displayed there. I'm not aware of any way of checking if an application is GPU bound though. – Billy ONeal – 2010-11-10T19:21:04.007

1@Billy: That's a pretty naive way of looking at it. Your CPU could be running at 99%, and the application could still be IO-bound by the hard drive. The OP is essentially asking if there is a way to measure this without just looking at the activity light and task manager and approximating. – Sasha Chedygov – 2010-11-10T23:36:09.567

@musicfreak: 1. the comment was appropriate before the question was edited. 2. I assumed "precise" measurements were not an issue because the OP doesn't have access to the source of the program, and is therefore not looking to profile it. 3. There is a reason I left the information in a comment instead of putting it into an answer. – Billy ONeal – 2010-11-11T02:23:18.673

@Billy: The fact that it's a comment and not an answer doesn't make it any better of a solution. As for precision, it definitely matters to a certain extent. You don't need to profile an application to figure out its bottleneck, but on the other hand, saying "just look at the task manager" is not precise enough. In the case of the CPU, for example, it doesn't tell you anything other than how much your CPU is being used, which, by itself, is pretty useless information. – Sasha Chedygov – 2010-11-11T04:02:23.697

@musicfreak: I don't understand how it's useless information. If the CPU is being maxed out, than it is a reasonable conclusion that the system in question is CPU (or the systems that support the CPU, such as the memory bus) bound. Without debugging symbols you aren't going to get anything accurate no matter what you're trying to do. – Billy ONeal – 2010-11-11T13:52:27.957

Like I said, the application can be memory-bound or IO-bound and still be using 99% CPU. And there are semi-accurate ways to measure bottlenecks without needing debug symbols, I just don't know if a tool made specifically for that purpose exists. I'm not saying you're wrong--profiling really is the only 100% accurate way of finding bottlenecks, but it's not the only way. You can look at how much time an application spends waiting on the hard drive or RAM or whatever. – Sasha Chedygov – 2010-11-11T20:46:38.843